The present invention relates to magnetic data transducing head sliders of the type supported aerodynamically during operation of a disk drive, and more particularly to a design for such a slider to reduce slider/disk friction and stiction, and support the slider in a desired orientation when in contact with a data storage disk.
In typical magnetic data storage devices, magnetic disks with flat recording surfaces are mounted rotatably, and magnetic data transducing heads are positioned in close proximity to the recording surfaces of the disks. Each transducing head is movable generally radially with respect to its associated disk. In higher capacity devices, the disks are rotated at high speeds to create an air cushion or bearing that supports each transducing head at a controlled distance from its associated recording surface. The transducing heads contact their associated disks only when the disks are either stationary, accelerating from a stop, or decelerating to a complete stop. In some drives, the accelerations and decelerations occur at power-up and power-down respectively, while in other drives the disks may undergo a deceleration and acceleration between two successive data operations. In either event, there is a need to support the transducing head slider at rest upon the associated recording surface.
Designers of magnetic disks continually strive to increase the density at which the magnetic data can be stored. One factor that limits storage densities is the transducing head flying height, i.e. its distance from the recording surface when supported by the air bearing. As discrete data storage areas are placed more closely to one another, the transistor must xe2x80x9cflyxe2x80x9d closer to the recording surface to distinguish between adjacent storage areas. In recent years, transducing head flying heights have been decreased from levels greater than about 10 microinches to levels of about 2 microinches. Flying heights of about 1.5 microinches and less are under consideration. These lower flying heights have been achieved largely due to improved techniques for reducing media surface roughness. However, the transducing head sliders exhibit a tendency to adhere to the extremely smooth media surfaces, a problem frequently referred to as xe2x80x9cstictionxe2x80x9d that can perturb the slider during disk accelerations, and in some cases lead to a catastrophic head crash.
To counteract this problem, disks with super smooth recording surfaces also have been textured to provide an annular dedicated landing zone or head contact zone with greater surface roughness than the data storage areas of the disk. Laser texturing of landing zones has been found particularly effective. See, for example, U.S. Pat. No. 5,062,021 (Ranjan et al) assigned to the assignee of this application. The Ranjan patent describes using a laser to form depressions surrounded by raised rims. Alternatively, international publications No. W097/07931 and No. W097/43079 describe forming domes or nodules. In either case, multiple texturing features cooperate to provide a controlled texture pattern throughout the dedicated contact zone.
At transducing head flying height on the order 1-2 microinches, the contrast in roughness between the data storage area and the textured contact zone raises concerns, because the peaks of the contact zone may protrude into a normal operating range of slider, increasing the risk of unintended and damaging slider/disk contact. Short of actual physical contact, a transducing head flying near the interface of the data zone and the textured zone may be perturbed by a buffeting of the air bearing over the laser nodules or other features. In addition, the annular area requiring texturing is relatively large compared to the air bearing surface of the slider, and occupies an area of the disk that otherwise would be available for storage of data. Further, in drives that use media with textured contact zones, the rotary actuator or other head supporting structure must be controlled to carry the transducing head into alignment with the contact zone in response to sensed decelerations of the disk, and further controlled during accelerations to maintain the head in alignment with the contact zone until satisfactory aerodynamic support is achieved.
Accordingly, it is an object of the present invention to provide a disk drive in which a disk or other recording medium can have a substantially uniform and negligible surface roughness over an entire area confronted by an aerodynamically supported transducing head.
Another object is to provide a magnetic data transducing head slider with an air bearing surface controllably textured to enable contiguous surface contact with extremely smooth media surfaces, to selectively orient the slider with respect to the media surfaces while maintaining acceptably low levels of friction and stiction.
A further object is to provide a process for selectively texturing the air bearing surfaces of magnetic data transducing head sliders.
Yet another object is to provide a data storage device with an aerodynamically supported transducing head slider adapted for surface contact with its associated data storage medium over an entire surface of the medium to eliminate the need to guide the slider to a particular zone of that surface.
To achieve these and other objects, there is provided a magnetic data transducing head slider, including a ceramic substrate body defining a generally planar air bearing surface having a nominal surface plane. A plurality of features are projected outwardly of the nominal surface plane. Collectively, the features are adapted to support the substrate body on a magnetic data storage medium with the air bearing surface in spaced apart relation to the data storage medium. The features are rounded and substantially free of sharp edges.
Such features are particularly well adapted for supporting the ceramic substrate body on an extremely smooth and planar recording surface of a data storage medium. The features substantially reduce the area of slider/medium contiguous surface engagement, to counteract stiction and considerably reduce dynamic friction during accelerations and decelerations of the storage medium with respect to the slider.
As can be appreciated by considering the aforementioned U.S. Pat. No. 5,108,781 and international publications No. W097/0793 1 and No. W097/43079, the selectively textured transducing head slider affords advantages similar to those achieved by selectively texturing data storage media to provide dedicated landing or contact zones. When transducing head sliders rather than media are textured, several further advantages arise. One is a substantial reduction in the required area that needs texturing, in particular the air bearing surface of the slider or a portion of the air bearing surface, as opposed to a contact zone""s complete circumferential extension and width at least equal to that of the slider. Texturing the slider eliminates the need for a contact zone on the disk or other data storage medium. As a result, additional surface area is available for storing data. Also, because the slider can come to rest against the medium virtually anywhere along the recording surface. There is no need to carry the slider to a landing zone or any other required location when decelerating the medium. Likewise, there is no need to maintain the slider aligned with a particular zone of the medium when accelerating the medium.
According to another aspect of the present invention, the slider supporting features are formed by a process for treating a ceramic substrate body of a magnetic data transducing head slider, including the following steps:
a. providing a ceramic substrate body having a substantially planar air bearing surface defining a nominal surface plane;
b. applying a heat-formable material to the ceramic substrate body along the air bearing surface; and
c. concentrating coherent energy at selected locations along the heat-formable material, forming at each selected location a feature of the material that projects outwardly beyond the nominal surface plane.
The features can be formed with a substantially uniform height or degree of projection beyond the nominal surface plane. As a result the features cooperate to support the ceramic substrate body with the nominal surface plane in substantially parallel, spaced apart relation to the recording medium. Alternatively the features can be selectively varied in size to form a height gradient in a selected direction across the slider. For example, larger features can be formed near a forward edge of a slider that supports a magnetic data transducer along its trailing edge. Then, the features support the slider with the nominal surface plane slightly inclined away from the data storage medium in the forward direction. More particularly, the slider body can be supported in an inclined orientation selected to simulate the in-flight orientation in which the air bearing supports the slider when the medium is moving relative to the slider. This reduces the tendency of the slider to experience rocking action from the transition to air bearing support that occurs during takeoffs.
The application of the heat-formable material is advantageous because concentrating laser energy on the ceramic substrate tends to ablate and/or remove material, rather than forming rims, nodules or other rounded features as desired. A metal, in particular chromium, is a highly preferred heat-formable material because of its good adhesion to the ceramic substrate material along with the formation of rounded rims or nodules when exposed to concentrated laser energy. Molybdenum, tungsten, NiFe alloys and copper are also acceptable heat-formable materials.
Under most circumstances it is preferred to utilize the heat-formable material in localized regions over the air bearing surface rather than in a continuous film entirely covering that surface. To this end, masking or etching techniques are employed to limit coverage of the heat-formable material. Further, it is advantageous to provide channels, pockets or other depressions to receive the heat-formable material, so that the outer surface of the material is substantially coincident with, or slightly recessed inwardly of, the nominal plane of the air bearing surface. Nonetheless, the chromium or other metallic regions are preferably uniform in their height or outward extent, so that any height gradient, to the extent possible, is solely the result of varying sizes of the nodules or other features.
Thus in accordance with the present invention, selective texturing of the transducing head slider, in particular over its air bearing surface, eliminates the need to provide a textured contact zone in the disk or other data storage medium. The entire slider-confronting surface of the disk can be extremely smooth, and available for storing the magnetic data. The nature of the air bearing and in-flight behavior of the slider are consistent over the entire surface increasing slider stability and reducing the risk of unintended contact with the disk. With the slider able to come to rest against the disk at any location over the recording surface, there is no need to guide the slider to any particular location before the decelerating disk comes to rest.